Understanding the Difference Between Autism and Intellectual Disability

It is often the case that many have a stereotypical view that Autism equates, to at least some degree, to intellectual disability. This is a particularly strongly held belief towards Autistic children / adults who communicate non-verbally. Often correlating with this false belief, is the equally damaging belief that the child / adult has limited ability to learn and will continue to have limited abilities across their life-span.

Clarifying between Autism and Intellectual Disability and / or their co-presence has important health, social, and cultural implications – greater and more widespread differentiation helps reduce stereotypes and stigmas and allows more focus on the specific support needs of an individual.

To better understand differentiation between Autism and Intellectual Disability, there are two terms that need to be understood:
1. Intellectual Ability – which describes an individuals ability to learn, reason, problem solve, plan, think abstractly and apply / transfer learnings.
2. Adaptive Ability – which describes the skills needed to live in an independent manner including communication, social skills and self-help skills.

‘Intelligence’ – the ability to acquire and apply knowledge and skills – is generally static / remains the same throughout a persons life-span; whereas ‘Developmental’ is the development trajectory of a child / adults development, and is not static throughout a person’s life-span.

Core differences between Autism and Intellectual Disability include:

• A person with Intellectual Disability (often defined as a formally assessed intelligence quota of 70 or less) has challenges with both Intellectual functioning and adaptive functioning; however social cogitation in Intellectual Disability is generally significantly less compromised than in Autistic individuals.
• Skill development in Intellectual Disability is usually slow but is at a relatively even pace across all spheres.
• A person on the Autism Spectrum has a different, uneven skill development trajectory in adaptive development – they may progress quickly and easily in some areas, and likely somewhat differently / unevenly in communication, social / emotional development, and language development.
• Inability to speak, does not mean inability to think, comprehend or learn – verbal ability, or inability, in itself, is not an indicator of Intellectual ability. Highly verbal individuals can have average intelligence or a co-existing Intellectual Disability; equally, a non-verbal individual may be assessed as having very high intellectual ability.
• A diagnosis of Autism Spectrum Disorder, Level 3 (previously known as Autistic Disorder / Classic Autism) does not, diagnostically, equate to the child having also been diagnosed with Intellectual Disability and / or having lower intelligence than their same age peers.
• Intelligence assessments generally assume competence in both language / communication, and ability to socially engage with the assessor – two core areas that Autistic children have different developmental trajectory (delay) in. For this reason, it is not uncommon for outcomes of intelligence testing of Autistic children – especially younger or pre-verbal children and / or children who communicate non-verbally – to result in ‘false positives’ (assessment outcomes determining a child as having intellectual disability, when they do not) – with those children later going on to achieve average, or above average results in future intelligence assessments.

A child who is both on the Autism Spectrum and has co-concurring intellectual disability, will likely present differently, learn differently and require different (and likely higher level) individual supports than an Autistic child who does not have co-occurring intellectual disability.

Very high level, complex needs, in this context, may not be consequent of Autism of itself, but rather consequent of the child having intellectual disability and / or the combined challenges of both Intellectual disability and Autism.
Identifying a co-concurring Intellectual Disability in an Autistic child is important to best support the individual learning needs and development of independence skills of that child. An Intellectual Disabled Autistic child will, for example, benefit from more repetition, including pre-teaching and re-teaching, particularly in intellectual functioning areas, compared to other Autistic children their age.

Importantly, presuming competence – that is assuming a person has capacity to think, understand and learn – is the only respectful path when interacting with both Autistic and / or Intellectually Disabled individuals. With the right supports, all individuals are capable of growing, learning and developing; and, all individuals, irrelevant of intellectual challenges, have their own personalities and preferences which should also be respected.

In a Nutshell …

1. Autism is not an Intellectual Disability. Intellectual ability (or deficits in Intellectual ability) is not part of the diagnostic criteria of Autism, and infact, never has been.
2. Autism does assume developmental delays in ‘Adaptive ability’, which often presents as a different, and generally uneven, developmental trajectory in social / emotional development, communication, language and self-help skills. Development is not static.
3. Intellectual Disability assumes challenges in an individuals ability to intellectually learn, acquire and apply skills, but does not equate to inability to learn.

Absence of differentiating strengths and challenges of Autistic neurology, from the strengths and challenges of an Autistic person’s innate personality is another area that often leads to confusion about Autism. Click here to read about the difference between Autism and Personality.